#!/bin/bash
#
# dont-go-there.sh
#
# From "Don't go there: Keeping the Unix 'find' command out of your CVS
# and Subversion directories."
#
# http://forwardlateral.com/blog/2006/02/27/dont-go-there/
# Copyright 2006 by Michael Birk, mbirk@forwardlateral.com
#
##########################################################################
#
# This is a wrapper around the standard external "find" utility, which
# automatically prunes Subversion and CVS metadata directories.
#
# It works by modifying the find expression to include an additional
# constraint.  This technique is complicated by the non-standard
# command-line syntax used by find.
#
# Installation is simple -- just source this file from your .bashrc or
# .bash_profile script.  For example:
#
#    source /path/to/dont-go-there.sh
#
# The script hides the external find command with a shell function of
# the same name, making the functionality transparent.
#
# As a special escape mechanism, if the (very) first argument to find is
# -debug, then it prints (to stderr) the modified find command line.  For
# example:
# 
#   > find -debug -name \*.sh
#   find . ! ( ( -name .svn -o -name CVS ) -prune ) -name *.sh
#
######################################################################
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
#
######################################################################
#
# Changes:
#   1.0 -- 2006 Feb 27 -- Initial Release
#
function find ()
{
    # If the very first argument (even before -H) is -debug, then print out
    # the complete find command before running it.
    local debug=0
    if [[ x$1 == x-debug ]]; then
        debug=1
        shift
    fi

    # Any initial -H, -L, or -P arguments must come at the beginning.  We 
    # will store the ones that we find in the "options" array.
    local -a section1
    while (( $# > 0 )); do
        local arg=$1
    
        # Push global options onto the "section1" array.
        if find_matches "$arg" "${find_global_options[@]}" ; then
            section1[${#section1[@]}]=$arg; shift
        
        # Otherwise move on to the next section.
        else
            break
        fi
    done

    # Next come the path names.  These are identified by the fact that they do
    # not start with a dash.
    #
    # Note that here we set a default value of the current directory.  So that 
    # this can be overwritten, we use a separate path_index to keep track of 
    # position.
    local -a section2=(.)
    local section2_index=0
    while (( $# > 0 )); do
        local arg=$1

        # Push paths onto the "section2" array.
        if [[ x${arg:0:1} != x- ]]; then
            section2[$((section2_index++))]=$arg; shift
        
        # Otherwise move on to the next section.
        else
            break
        fi
    done

    # Finally we have the expression, which starts with various options,
    # each beginning with the dash.  However, there are several "special"
    # options that must come at the beginning, before our inserted condition
    # for pruning directories.  We simply append them to the "paths" array as
    # well.
    while (( $# > 0 )); do
        local arg=$1
        local param=$2

        # If this is a special option (with or without parameters), then move
        # it to the paths array.
        if find_matches "$arg" "${find_special_options[@]}"; then
            section2[$((section2_index++))]=$arg; shift
        
        elif find_matches "$arg" "${find_special_param_options[@]}"; then
            section2[$((section2_index++))]=$arg   ;shift
            section2[$((section2_index++))]=$param ;shift
            
        # Otherwise move on to the next section.
        else
            break
        fi
    done

    # Anything left is the expression, which goes at the end, after the
    # inserted $find_options.
    find_debug $debug find "${section1[@]}" "${section2[@]}" $find_options "$@"
}

# Simple helper function to optionally print the command line before
# executing it.  Used when the -debug option is given.
function find_debug ()
{
    local debug=$1; shift
    if (( $debug )); then echo "$@" 1>&2; fi
    command "$@"
}

# Returns 0 if the first argument matches any of the remaining arguments,
# 1 otherwise.
function find_matches ()
{
    local value1=$1; shift
    local value2
    for value2 in "$@"; do
        if [[ x$value1 == x$value2 ]]; then return 0; fi
    done
    return 1;
}

# New options that are inserted after any "special" options (such as -depth),
# but before the "normal" expression (e.g. -name).
find_options="! ( ( -name .svn -o -name CVS ) -prune )"

# Global options that must go up-front, before any paths (but after our
# synthetic -debug option).
find_global_options=(
    -H
    -L
    -P
)

# "Special" options that should go at the front of the expression.  If one 
# of these is not at the front, the external find command issues a warning.
find_special_options=(
    -daystart
    -d
    -depth
    -follow
    -help
    --help
    -ignore_readdir_race
    -mount -noignore_readdir_race
    -noleaf
    -version
    --version
    -xdev
)

# These are "special" options that also take a single parameter, which
# immediately follows it.
find_special_param_options=(
    -maxdepth
    -mindepth
    -regextype
)